Photographic developer element



July 3, 1951 E. H. LAND 2,558,857

PHOTOGRAPHIC DEVELOPER ELEMENT Filed Feb. 8, 1947 FIG. I

CooIing of Liquid Composifion) (I2 Image Carrying Layer Oxygen and WoIer Vapor Impervious Cocxfing FIG. 2

Base Layer (PhoIosensHive Layer Pressure Roller so FIG. 3

Impervious Coaflng FIG. 4

Patented July 3, 1951 UNITED STATES PATENT OFFICE Edwin H. Land, Cambridge, Mass, assignor to Polaroid Corporation, Cambridge, Mass, a corporation of Delaware Application February 8, 1947, Serial No. 727,381

11 Claims. 1

This application relates to photography and more particularly to novel photographic materials.

A principal object of the present invention is to provide a novel composit sheet material for use in photography which, when contacted with a layer of photosensitive material, is capable of developing a latent image in said photosensitive material and producing a positive image of said latent image on the surface of said sheet material.

Another object of the present invention is to provide a novel sheet material of the above type containing a layer of viscous liquid composition coated upon a layer of a material which is substantially impervious to oxygen and water vapor or has been so treated as to increase its impermeability, and said sheetlike material is capable of being formed into a substantially water vapor and oxygen impervious package such as a roll.

Another object of the present invention is to provide, for use in a composite sheet material of the type mentioned above, a layer of a viscous liquid composition having such dimensional stability as to be capable of completely maintaining its filmlike characteristics under conditions of use and containing a sufficient quantity of water to maintain the reactive portions of said liquid composition in solution.

For a fuller understanding of the nature and objects of the invention, reference should be had to the accompanying drawings wherein:

Figure 1 is a somewhat diagrammatic, transverse sectional view of one type of sheet material comprehended by the present invention;

Fig. 2 is a diagrammatic, sectional view of the novel sheet material of Fig. 1 in contact with a photosensitive layer to show a preferred use of the present invention;

Fig. 3 is a diagrammatic sectional view of a package containing the novel composite sheet material of Fig. l in a roll form; and

Fig. 4 is a plan view of a portion of the novel composite sheet material showing another modification of the invention.

In general, the invention relates to a novel sheet material having thereon a very viscous coating comprising a liquid composition including a developer and a silver halide solvent, which, when contacted with an exposed photosensitive layer, is capable of developing a latent image in said photosensitive layer and forming a silver positive image of said latent image in said liquid coating. The liquid composition has such viscosity as to form a ,very stable coating having the physical 20 carrying layer.

45 waxes have this characteristic.

characteristics of a solid while containing a sumcient quantity of water so that it retains the chemical characteristics of a solution. The viscosity of the material is also so high as to have an increased impermeability to oxygen.

The novel liquid composition and the novel composite sheet material formed therewith are particularly adaptable for use in a one-step photographic process wherein a positive image of a subject image is obtained from a latent negative in a photosensitive layer within a camera. This novel material may be readily rolled into an oxygen and water vapor impervious package from which it can be uncoiled so as to be placed in contact with an exposed photosensitive layer.

Referring now to Fig. 1, there is shown a preferred modification of the invention wherein there is provided a layer H] of material such as paper which is hereinafter referred to as an image- This image-carrying layer, in a preferred embodiment, is formed of a sheet of paper known in the art as baryta paper.

On one side of the sheet of baryta paper Hi there is an oxygen and water vapor impervious coating 14 such as a wax, a plastic, or a metal foil, such as lead or tin foil, or a combination of several of such materials. A preferred oxygen and water vapor impervious backing 14 for the image-carrying layer I0 is formed by contacting the back side of the layer ill with a bath of melted "Product 2305, by American Cyanamide and Chemical Corp. under the designation Ozakerite yellow wax, by Quaker State under the designation White 5A Wax 160/ 1'70, by the Boreco Oil Co. under the designation Be Square Special 170/175 White.

In some cases it is desirable to have the wax, or other material used in the coating [4, permeate into the pores of the baryta paper to increase the density and impermeability thereof. The above On the other side of the baryta sheet Ill there is provided a coating l2 of a liquid composition having a very high viscosity and containing a developer, a silver halide solvent, a cellulosic film-forming material,

and an alkali. This liquid composition l2 has a sufiicient quantity of water therein so that the various elements, particularly the developer, etc., are in solution. Some of the film-forming material may be in solution. The important point is that there is enough water in the liquid composition to carry the reactive elements, such as the developer and the silver halide solvent, in solution so as to impart to the liquid composition the chemical characteristics of a solution.

The viscous liquid composition l2 may be formed as set forth in the following nonlimiting examples:

Example 1 are added in dry form: 14.9 grams of citric acid, H

19.6 grams of hydroquinone, and 29.4 grams of sodium sulfite. This is then mixed into the first portion of the liquid composition for another hour. During this mixing, the temperature of the liquid composition is kept at approximately 34 to 35 degrees centigrade and a sufficient vacuum is applied to the mix to remove all air from the mixture so as to prevent oxidation of the components of the mix during the mixing time.

Example 2 The following ingredients are mixed in a mechanical mixer in a manner'similar to that described in Example 1:

Sodium. carboxymethyl cellulose (high viscosity it 1672, Hercules) grams 58 Water cc 800 Sodium hydroxide grams 36.1 Sodium thiosulfate do 7.0 Citric acid do 19.1 Sodium sulfite do 37.8 Hydroquinone do 25.2

Such liquid compositions are extremely viscous, having. the consistency of a very thick jelly. The liquid composition may be coated on the image-carrying layer II] by means of usual coating techniques such as by the use of pressure coating rolls. It is preferred that this coating operation be carried out in an inert atmosphere so as tov prevent oxidation of the developer in the liquid composition. It is possible, however, to form this coating without special precautions in view of the fact that the material is so viscons that oxygen seems to be incapable of permeating it, and whatever oxidation does occur is primarily a very slight surface oxidation. However, the sheet material should be coiled upon itself immediately after coating and formed into an oxygen and water vapor impervious roll. When such a roll is formed, the only places where oxygen can enter, or water vapor escape, are the edges of the roll. These edges are preferably sealed such as by having a coating of wax or other oxygen and water vapor impervious material applied thereto. A portion of the leading end of the image-carrying layer ill may be left uncoated so that this uncoated portion may act as a leader for positioning the sheet material in a camera.

When the package is mounted in a camera it is positioned preferably so that the coating 52 is contacted with the photosensitive emulsion of an exposed photosensitive film. These two surfaces are preferably brought into intimate relationship by the application of pressure thereto. In Fig. 2 this step of the photographic process is shown diagrammatically.

As shown in Fig. 2 there is provided the image-carrying layer I 0 having on its surface a layer of liquid composition 52 and having on its back the oxygen and water vapor impervious coating M. This composite sheet material has been brought into contact with a layer of photosensitive material Ill carried by a usual cellulosic film base 16. Composite sheet material l9, l2, I4 is pressed in contact with the photographic film IS, It by means of a pair of pressure rollers 24. It is not essential to apply this pressure but it is desirable since it assures intimate contact between the surface of the layer of liquid composition and the photosensitive emulsion l8. If this intimate contact is not obtained, the final image is apt to be imperfect, since any spaces between the surface of the layer l2 and the surface of the layer it prevent the passage of the developer, and the other materials in solution, from the liquid layer i 2 to the photosensitive layer 58. When the materials are in the positions shown in the right-hand portion of Fig. 2, the liquid composition permeates the photosensitive emulsion l8 and the developer therein develops the latent image. The silver halide solvent, concurrently therewith, forms soluble silver complexes with the undeveloped silver halide and transfers these soluble silver complexes to layer l2 where they are converted to an image comprising silver by the developer remaining in the layer 52. There is thus produced in the liquid layer a positive image of the latent negative image. This layer is considerably dried out by contacting the photosensitive layer, since the gelatin of the photosensitive emulsion acts to absorb a considerable amount of the water from the liquid composition, the film-forming material dissolved in the liquid composition precipitates from the liquid composition and forms a dimensionally stable film containing the positive image. When the novel sheet material, having thereon the layer of film-forming material, is separated from the photosensitive layer after a time of one or two minutes, the remainder of the water in the liquid composition evaporates and the film becomes completely dry.

There are certain attributes which are desira ble in the layer E2 of the liquid composition. It should have such dimensional stability that the thickness of the film in any particular portion thereof will remain constant during the normal usage of the film. Also, it should not spread when placed under a considerable pressure in the neighborhood of several pounds per square inch. It is also preferable that the film be only slowly permeable to oxygen so that very little oxidation of the developer contained therein will occur in the time between the transfer of the sheet assembly from an oxygen impervious assembly, such as a roll thereof, to intimate contact with the photosensitive layer 18. The film of liquid composition must also be permeable to water so as to permit the transfer of the water solution of the developer and other materials from the film E2 to the photosensitive layer ii! for reaction therewith. It has been found that a liquid composition prepared in the manner discussed above and having a viscosity such that it will not cold flow under normal temperature conditions exhibits these desirable characteristics.

One of the principal advantages of the use of a composite sheet material of the type described above is that it permits a very accurate determination of the amount of developer and other materials which are available for reaction with any particular portion of the photosensitive layer I8. It is thus possible to control the amount of developer so that the amount of developer available for reaction with any unit area of the photosensitive layer l8 is just suihcient to completely react with a fully developable unit area of photo sensitive layer I8. In case it is desirable to use more than this amount of developer, which is preferable in some instances where a greater depth of image is desired, it is much simpler to determine by empirical analysis a proper quantity of additional materials which should be included in the liquid composition to prevent staining of any excess unreacted developer remaining in the layer l2 after the formation of the positive image is completed. The accurate control of the amount of developer available makes simpler the control, in accordance therewith, of the amount of a material such sulfite which is most desirable for preventing staining due to the presence of excess developer. The thickness of the laye i2, with any particular concentration of elements in the liquid composition, controls the quantity of each of these materials available for the reaction in any particular unit area. By the use of such a dimensionally stable film of the liquid composition, the quantities of materials available may be very closely controlled in the manufacture of the sheet material and it is not necessary to resort to careful controls in the camera for accomplishing the desired spreading of the liquid composition in the optimum film thickness.

The construction and physical characteristics of the assembly described in connection with Figs. 1 and 2 are of particular advantage since they enable the storage of such a sheet material in an oxygen and wate vapor impervious package from which it may be easily removed in a camera without subjecting the remainder of the package to permeation by oxygen or water vapor. In Fig. 3 there is shown a preferred method of storing such a sheet assembly in an oxygen and water Vapor impervious package. As shown in this figure, one end of a strip of the sheet assembly of Fig. 1 is attached to the spindle 32 of a roll of the type well known in photography. The assembly is then wound on this spool, building up a number of layers of the assembly on top of each other. In view of the oxygen and water vapor impervious coating is on the back of the sheet assembly, oxygen and water vapor cannot penetrate through the sheet assembly. Due to the fact that the dimensional stability of the film permits a tight roll to be made, there will be substantially no spaces remaining between the layers of the roll, and oxygen cannot enter, to any considerable degree, from the edges, nor can water vapor escape therefrom. However, as an added protection, particularly where a considerable time will elapse between the formation of the package and the use of the assembly, it is desirable to coat the edges of the roll with an oxygen and water vapor impervious coating such as wax, or a metal foil coated with wax, or other plastic, thus forming a completely sealed package. As the sheet assembly is fed from the roll shown in Fig. 3, only that portion of the seal 30 adjacent the layer being fed from the roll is broken; the remainder of the seal remains intact to protect the inner layers of the liquid composition from oxidation or water evaporation.

In some cases it may be desirable to dispense with the edge coating of the type shown in Fig. 3 at 30, in which case suitable oxygen and water vapor impervious strips may be formed on the marginal portions of one or both surfaces of the image-carrying layer while it is in a sheetlike condition so that, when it is rolled upon itself, these strips edge seal the image-carrying layer to the back of the precedin y r. As shown in Fig. 4, there is provided the usual image-carrying layer I!) which has a backing (not shown) of a water vapor and oxygen impervious material. On the marginal portions of the image-carrying layer there is provided a strip 48 of a sealing material which may be, in a preferred modification, a plastic adhesive, such as ethyl cellulose, a polyvinyl acetal known by the trade name Alvar, the polyvinyl butyral identified as Butvar, and the polyvinyl formal identified as Formvar. Between the adhesive strips 40 there is provided, on the surface of the image-carrying layer l0, a layer [2 of the liquid composition described above. When this sheet assembly is formed into a roll, the adhesive strips 43 thoroughly seal one layer of the roll to the next inner layer of the roll to form an oxygen and water vapor impervious seal. In some cases it may be desirable to extend the strip 40 completely around the edge of the imagecarrying layer [0 and onto the back surface thereof so as to form a complete seal around the edge of the assembly, thus preventing oxygen from entering the package through the edge of the image-carrying layer It This modification of the invention is desirable in those cases where the image-carrying layer I0 is formed of a relatively permeable material such as paper. Instead of having the seal 40 extend around the edge of the image-carrying layer II the backing for the image-carrying layer may be extended around the edge and brought to the front of the image-carrying layer. A further seal may be applied to the package, such as by dipping the sealed package into a bath of melted wax.

While the above invention has been described with particular reference to the preferred materials and the preferred construction of the film unit, it is apparent that many modifications thereof may be made without departing from the scope of the invention.

In place of the baryta paper which has been described as the preferred image-carrying layer ID, numerous other materials may be used such as other papers, cellulosic films, gelatin, polyhydroxy alkanes, such as polyvinyl alcohol, sodium alginate, cellulose ethers, such as methyl cellulose or their derivatives, such as sodium carboxymethyl cellulose or hydroxyethyl cellulose, cellulosic esters, such as cellulose acetate, cellulose nitrate, cellulose acetate propionate or cellulose acetate butyrate. In those cases where the liquid composition does not normally adhere readily to such an image-carrying layer, the image-carrying layer is preferably treated mechanically or chemically so as to increase the adhesion between the image-carrying layer and the layer of the liquid composition. The liquid composition should tend to adhere to the image-carrying layer I 8 more readily than it adheres to the back thereof or to any protective backing which has been applied to the image-carrying layer.

It is also possible to modify the components of the liquid composition 12 by utilizing a different developer, a different alkali, and substituting other equivalents for the other elements thereof. The film-forming material may be sodium alginate, hydroxyethyl cellulose, starch, gums or other materials, or mixtures thereof where such materials are capable ofv maintaining their viscosity over long periods of time at the alkalinity ofthe solution. The film-forming material may include an inert pigment material such as titanium dioxide so as to make said layer of liquid composition white and opaque. This latter modification is referred in those cases where the image-carrying layer l0, and any protective backing applied thereto, are transparent, since the white opaque characteristic of the liquid composition enables it to form a background for the positive image created in terms of black silver.

This white pigment may, in one preferred form of the invention, comprise zinc sulfide particles which have the ability of having their surface cations replaced by silver, from a silver complex, thereby converting the particles to black silverplated particles.

In another preferred form of the invention the sodium hydroxide may be omitted from the liquid and the liquid coated over a sub-layer of a sub stance of acid reaction, such as an acid, or acid salt. Such a subcoat is preferably a polymeric acid such as cellulose acetate hydrogen phthalate or carboxymethyl cellulose, these polymers being relatively insoluble at a low pH. In such a modification of the invention, the alkali is preferably associated with the photosensitive layer so as to be dissolved as the liquid permeates this latter layer. This last modification of the invention permits the storage of the liquid at a low pH, the development of the negative and positive images at a high pH, and the subsequent neutralization of the alkali for preventing staining due to excess developer. When an acid salt is used in place of the acid, a metal salt which forms a relatively insoluble metal hydroxide, such as lead acetate or zinc nitrate, is preferred.

Since certain changes may be made in the above product without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. As a new product for successively treating separate image areas of a silver halide emulsion to form transfer prints of latent images in said emulsion, an elongated flexible composite sheet wound into a roll so that the inner surface of each winding engages the outer surface of the preceding winding, said flexible composite sheet comprising an elongated supporting strip which is the outer layer of each winding of the roll and which has adhered to the inner surface thereof a liquid-containing layer of the consistency of very thick jelly, said supporting strip having between the inner and outer surfaces thereof a stratum substantially impervious to water and to water vapor, which stratum prevents depthwise diffusion of the liquid of said liquid-containing layer outwardly of said roll, and liquid-confining means cooperating with the edges of said composite sheet for producing a liquid-tight seal at each end of said roll which prevents edgewise escape of the liquid of the liquid-containing layer, the outer surface of said supporting strip having very little affinity for the said liquid-containing layer so that each winding is strippable from the next succeeding winding of the roll, said liquid-containing layer comprising a silver halide developer, a silver halide solvent and water, said water being in suflicient' quantity to provide all the water required to render said developer and said solvent operative, when said liquid-containing layer is brought into contact with a silver halide emulsion, to develop a latent image in said emulsion and to dissolve from the unexposed portions of said emulsion sufiicient silver to form a print of said latent image within said liquid-containing layer, said liquid-containing layer containing a sufficient amount of solid material to impart thereto its jellylike consistency.

2. The product of claim 1 wherein the impervious stratum of the supporting strip is a layer of microcrystalline wax.

3. The product of claim 1 wherein the impervious stratum of the supporting strip is a metal foil.

1. The product of claim 1 wherein the liquidconfining means comprise a material impervious to water and water vapor coated on each end surface of the roll.

5. The product of claim 1 wherein the liquidconfining means comprise a pair of sealing strips of a water-inipervious material mounted on the inner surface of the supporting strip and extending lengthwise thereof, adjacent the marginal edge portions thereof, on opposite sides of said liquidcontaining layer.

6. The product of claim 5 wherein the sealing strips are approximately as thick as the thickness of the liquid-containing layer.

'7. The product of claim 1 wherein the liquid in the liquid-containing layer is non-alkaline and the supporting strip includes a liquid-permeable surface portion which contains a material of acid reaction.

8. The product of claim 7 wherein the material of acid reaction is a polymeric acid.

9. The product of claim 1 wherein the liquidcontaining layer forms a transparent solid film when the liquid is removed therefrom and the inner surface of the supporting strip is white.

10. As a new product for successively treating separate image areas of a silver halide emulsion to form transfer prints of latent images in said emulsion, an elongated flexible composite sheet wound into a roll so that the inner surface of each winding engages the outer surface of the preceding winding, said flexible composite sheet comprising an elongated supporting strip which is the outer layer of each winding of the roll and which has adhered to the inner surface thereof a liquid-containing layer of the consistency of very thick jelly, said supporting strip comprising a layer of paper impregnated with microcrystalline wax, said microcrystalline wax providing a stratum substantially impervious to water and to water vapor and preventing outward diffusion of the liquid of the liquid-containing layer of each winding of said roll, the liquidconfining means cooperating with the edges of said composite sheet for producing a liquid-tight seal at each end of said roll which prevents edgewise escape of the liquid of the liquid-containing layer, the outer surface of said supporting strip having very little afiinity for the said liquidcontaining layer so that each winding is strippable from the next succeeding winding of the roll, said liquid-containing layer comprising all of the material, including a silver halide developer, a silver halide solvent and water, required to render said liquid-containing layer operative, when the latter layer is brought into contact with a silver halide emulsion, to develop a latent image in said emulsion and to dissolve from the unexposed portions of said emulsion sufficient silver to form a print of said latent image within said liquid-containing layer, said liquid-containing layer containing a sufficient amount of solid material to impart thereto its jellylike consistency.

11. The product of claim 10 wherein the solid material which imparts the jellylike consistency to the liquid-containing layer is a high molecular weight plastic.

EDWIN H. LAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,207,042 Hochstetter Dec. 5, 1916 1,261,748 McCurdy Apr. 2, 1918 1,911,955 Heinecke May 30, 1933 2,221,873 Knoefel Nov. 19, 1940 2,312,854 Toland Mar. 12, 1943 2,352,014 Rott June 20, 1944 2,360,216 Filius Oct. 10, 1944 OTHER REFERENCES Liesegang: Photographische Correspondenz," 1898, pages 9 and 10 cited (copy in S. L.).

Bullock: Chemical Reactions of the Latent Image, D. Van Nostrand Co., 1927, pages 13, 15, 145 and 146 cited. 

1. AS A NEW PRODUCTS FOR SUCCESSIVELY TREATING SEPARATE IMAGE AREAS OF A SILVER HALIDE EMULSION TO FORM TRANSFER PRINTS OF LATENT IMAGES IN SAID EMULSION, AND ELONGATED FLEXIBLE COMPOSITE SHEET WOUND INTO A ROLL SO THAT THE INNER SURFACE OF EACH WINDING ENGAGES THE OUTER SURFACE OF THE PRECEDING WINDING, SAID FLEXIBLE COMPOSITE SHEET COMPRISING AN ELONGATED SUPPORTING STRIP WHICH IS THE OUTER LAYER OF EACH WINDING OF THE ROLL AND WHICH HAS ADHERED TO THE INNER SURFACE THEREOF A LIQUID-CONTAINING LAYER OF THE CONSISTENCY OF VERY THICK JELLY, SAID SUPPORTING STRIP HAVING BETWEEN THE INNER AND OUTER SURFACES THEREOF A STRATUM SUBSTANTIALLY IMPERVIOUS TO WATER AND TO WATER VAPOR, WHICH STRATUM PREVENTS DEPTHWISE DIFFUSION OF THE LIQUID OF SAID LIQUID-CONFINING MEANS OUTWARDLY OF SAID ROLL, AND LIQUID-CONFINING MEANS COOPERATING WITH THE EDGES OF SAID COMPOSITE SHEET FOR PRODUCING A LIQUID-TIGHT SEAL AT EACH END OF SAID ROLL WHICH PREVENTS EDGEWISE ASCAPE OF THE LIQUID OF THE LIQUID-CONTAINING LAYER, THE OUTER SURFACE OF SAID SUPPORTING STRIP HAVING VERY LITTLE AFFINITY FOR THE SAID LIQUID-CONTAINING LAYER SO THAT EACH WINDING IS STRIPPABLE FROM THE NEXT SUCCEEDING WINDING OF THE ROLL, SAID LIQUID-CONTAINING LAYER COMPRISING A SILVER ALIDE DEVELOPER, A SILVER HALIDE SOLVENT AND WATER, SAID WATER BEING IN SUFFICIENT QUANTITY TO PROVIDE ALL THE WATER REQUIRED TO RENDER SAID DEVELOPER AND SAID SOLVENT OPERATIVE, WHEN SAID LIQUID-CONTAINING LAYER IS BROUGHT INTO CONTACT WITH A SILVER HALIDE EMULSION, TO DEVELOP A LATENT IMAGE IN SAID EMULSION AND TO DISSOLVE FROM THE UNEXPOSED PORTIONS OF SAID EMULSION SUFFICIENT SILVER TO FROM A PRINT OF SAID LATENT IMAGE WITHIN SAID LIQUID-CONTAINING SUFFICIENT AMOUNT OF SOLID MATERIAL TO IMPART THERETO ITS JELLY CONSISTENCY. 